The phenolic extractives in southern red oak (Quercus falcata Michx. var. falcata)

Abstract

The bark of southern red oak (Quercus falcala Michx. var. falcala) is a rich source of quercitrin (quercetin-3-rhamnoside). It contains only low concentrations of (+)-catechin and no significant amounts of epicatechin or gallocatechin. The three major dimeric proanthocyanidins present are epicatechin-(4β→8)-catechin, catechin-(4α→8)-catechin and the 3-gallate ester of epicatechin-(4β→8)-catechin. No biphenyl-linked dimers and no flavan-3-ol- or proanthocyanidin-glycosides are evident. The higher molecular weight acetone-water soluble tannins are polymeric procyanidins predominantly made up of 2,3-cis chain extender units and terminated with the 2,3-trans (+)-catechin. The polymers contain only small amounts of 2,3-trans procyanidins chain extender units and only traces of prodelphinidin units. Although a gallate ester of a dimer is present in significant amounts, neither gallate esters of higher molecular weight procyandins nor hydrolysable tannins are detectable through reaction products or IR and ¹³C-NMR spectral studies.

Citation

Ohara, Seiji; Hemingway, Richard W. 1989. The phenolic extractives in southern red oak (Quercus falcata Michx. var. falcata). Holzforschung 43(3):149-154